Priority is claimed with respect to European Patent Application No. 00810430.9-2304 filed on May 17, 2000, in the European Patent Office, the disclosure of which is herein incorporated by reference.
The invention relates to a device for delivering a printing plate to a plate cylinder of a printing press in a position ready for exchange where one printing plate edge can be transferred to a holding fixture on the plate cylinder.
A known device of this type, disclosed in EP 0 714 771 A2, comprises a linear drive for gripping devices arranged on the printing press machine frame near the plate cylinder. These gripping devices can be advanced tangentially toward the plate cylinder. A suspension bar supported on pivoting arms extends parallel to the axis of rotation of the plate cylinder. The front edge of the printing plate to be secured is suspended from the suspension bar in a position where it can be pivoted for transferring the printing plate. The suspension bar is subsequently pivoted in the direction of the plate cylinder, thus moving it into the movement path of the gripping devices. The gripping devices guide the printing plate with its angled, front edge to an axial plate channel of the holding fixture, formed in the outer periphery of the plate cylinder. As a result, the printing plate with its angled edge can be secured tightly in the plate channel. The plate cylinder with the secured front edge of the printing plate is then rotated. The printing plate is consequently wound onto the printing cylinder until its rear edge, which is also angled, engages and is secured either in the same plate channel of the front edge or in a different one.
Another known device, disclosed in EP 0 567 754 A1, is provided with a roller and, at a distance thereto, a suction cup is arranged on a section of a printing mechanism guard on the printing press, which can be tilted upward. The printing plate to be secured is supported on the roller and held in place by the suction cup. When the hinged-on printing mechanism guard is in the tilted-up position, the section that supports the roller and the suction cup is positioned in such a way, relative to the plate cylinder, that the printing plate held by the roller and the suction cup is aligned tangential to the plate cylinder and can be supplied correctly positioned to its holding fixture.
A known method of storing the printing plate to be secured inside a magazine, disclosed in DE 195 08 844 A1, is provided with transporting means for pushing out the printing plate. Relative to the plate cylinder, this magazine is arranged on the printing press in such a way that the printing plate, which is pushed out by the transporting means, is placed with its front edge into the correct position for securing it in the holding fixture of the plate cylinder.
All of these conventional devices require that the position for exchange, in which the front edge of the printing plate to be secured is transferred to the holding fixture of the plate cylinder, is clearly determined. The conventional devices are therefore designed only for a single printing plate format and size. Plate cylinders for different printing plate formats, however, have different diameters. As a result, the holding fixtures for the plate cylinders with different diameters occupy correspondingly different positions in the printing press.
It is an object of the invention to create a device of the aforementioned type, which permits the operation with different formats.
The above and other objects are solved according to the invention by assigning a number of exchangeable format slide-in units to the printing press. These units can be inserted optionally into the printing press and accommodate the respective plate cylinder with a diameter corresponding to the selected format. The delivery mechanism is provided with a number of settings that correspond to the number of format slide-in units and determine the position of exchange that corresponds to the respectively inserted format slide-in unit.
The format slide-in units are designed to fit into a specially provided receptacle on the printing press and are driven by the latter, independent of the format dependent diameter of the plate cylinder. The plate cylinder, the rubber cylinder engaged therewith and, if necessary, a counter pressure cylinder that meshes with the rubber cylinder are respectively positioned inside the format slide-in units. The rotational axes for these cylinders and their cylinder jackets occupy different positions in the various format slide-in units because of the format dependent different radii. According to the invention, the different settings of the delivery mechanism take into account the correct changing position for the respective printing plate to be secured for each inserted format slide-in unit.
According to a particular embodiment of the device according to the invention, a positioning element determines the setting on each format slide-in unit for an opposing element. The opposing element, which can be made to engage in the positioning element, is provided on a printing plate guide element that aligns the outer edge of the printing plate to be secured. During a format change, only the printing plate guide element must be released from the engagement between its counter element and the positioning element for the format slide-in unit to be exchanged. Following the insertion of the new format slide-in unit, it must again be made to engage with its positioning element. For this, the printing plate guide element can be suspended freely moving on a suitable support device, so that its inherent weight is essentially supported during this operation and is available within grasping distance of the printing press, even in the state where it is not engaged with the positioning element.
The positioning element for the aforementioned embodiment of the format slide-in unit delivers the necessary position information for the respective setting of the delivery mechanism. In contrast, a holding fixture 28 (FIG. 2) can be provided according to an alternative embodiment, which is supported on a stationary section accommodating the format slide-in unit, in particular on the printing press. This holding fixture is connected with one free end to a printing plate guide element that aligns the edge of the printing plate to be secured and has an adjusting mechanism 30 (FIG. 2) for the number of settings for the free end that correspond to the positions for exchange. In that case, the adjusting mechanism for the holding fixture contains the information necessary to determine the appropriate positions of exchange for the various format slide-in units. This adjusting mechanism could be an articulated mechanism, for example, which snaps into various angular positions that correspond to the positions for exchange.
In that case, a manual selection of the appropriate setting on the adjusting mechanism by an operator exchanging the respective format slide-in unit does not result in a special expenditure. However, the embodiment can conceivably be modified in such a way that the printing press is provided with a sensor 32 (FIG. 2) for detecting the respectively used format slide-in unit, as well as an actuator for the automatic selection of the respective setting in response to the detection signal from the sensor.
The printing plate guide elements for the aforementioned embodiments, which may include one or several guide rollers on a support frame that can change position, function to correctly align the edges of the printing plates to be secured. In another modification of the invention, this guide element is designed such that it can be moved from the respective position of exchange to a stand-by position. The guide element is removed from the printing press in this stand-by position relative to the changing position. This permits good access during the format exchange, an unobstructed course for the printed pages during the printing operation and, at the same time, an easier loading of a new printing plate.